BFD plot, after 2 weekends I'm finally getting somewhere.

[kexodusc]

I've had this thing since mid-March, but last weekend (June 11) was the first time I could hook it up and fiddle around with it.

I have to say, this thing is worth every penny, I no longer have a big room induced suckout and bottom end boom, which has allowed me to turn the sub up without the annoying bass peaks. I had a difference of over 24 dB between my biggest peak and dip. Let's say a response +/- 12 dB...pretty bad. Now it's about +/- 5 dB. The graph doesn't include all actual measurements, there' s a 3 points in particular where my response still varies by 5 dB but I just never bothered to modify the spreadsheet.

On that note, my in room results are pretty odd....most on-line node/mode calculator's I've seen predict different behavior. I attribute this to the 2 doors, 2 windows, and half-foot countersunk walls along 1/2 the room...maybe sub position as well...anyway.

The BFD is as frustrating to learn at first as everyone mentions. But half an hour or so everynight and a few afternoons on weekends goes a long way.

My reference level was 64.5 dB, though I had originally done these at 80 and 70 dB. As I'd hoped, the results were pretty much linear except the dips were a bit lower relative reference at higher SPL. I chose the lower volume because there were too many buzzes and rattles adding a dB or two at some frequencies.

I would like to lower this curve overall by 1 or 2 dB, but it's not as simple as the knob on my sub amp or the receiver settings for some reason.

I'm definitely going to aim for the "house-curve, boosting frequencies below 40 Hz or by about 6 dB per octave, my hearing definitely drops off a bit down that low. I suspect I'll have to start all over again - it's unreal how boosting or cutting low frequencies affects the higher ones. I'll basically have to increase the gain on my amp and cut the frequencies above 40 Hz I think.

I'm also going to have to try all this again with the Radio Shack SPL meter if I ever get it back from my brother.. My Galaxy Audio SPL meter is much more accurate above 40 Hz, I'm not so sure about below that point though, and it'd be nice to double check.

All in all, this could be the best purchase in my home theater system to date. You really can't explain how much bass you are missing (or adding) once you tighten up the in-room response. I've also increased my crossover from 60 Hz back up to 80Hz because, well, it sounds alot better, the 15" sub doesn't betray it's location too much, and more consistent response is well worth the trade-off. Surprisingly this benefits multi-channel audio more than movies (probably because of bass management issues).

At $100 if you're still on the fence, go ahead and get one of these. It's a damn cheap upgrade that dramatically improves 2 or 3 octaves of info, and lets you squeeze the most out of your sub.

The blue curve is the measured in room response without the parametric eq, the pink curve is with parametric eq, the yellow is the reference level.

[hmmmm]

Well, since there is no such thing as a stupid question...do you have a software program that works with the BFD that prints out the graph? I still haven't purchased one because it does seem like a pain to set up.
Also, have you noticed when you play DVD-A and SACD, your system doesn't play as loud? Since we have about the same setup I was curious to know.

[kexodusc]

There is software you can download, however, it really isn't that bad. If you can build a speaker and sub, you can figure this thing out. Not to mention there's 47 years of experience with this unit lurking here on the forums, that's all the help you'd ever need.

If you have a Radio Shack SPL meter, download some test tones and check out the response of your sub between 20 and 90 Hz. You'll be surprised what room acoustics do. If your response curve is as bad as mine was (or heaven forbid, worse), you owe it to yourself.

I do lose a couple of dB's from my cheapo Toshiba DVD-A/SACD player. That's normal though, probably just a different output sensitivity (ie: voltage). My Arcam CD player is also a bit louder than most of my other units. So is my X-Box.

Don't worry about turning up your receiver any, the numbers in the display are arbitrary and don't necessarily mean that the amplifiers are at max.

[Geoffcin]

You had a 20dB slope over ~30 hz?! That is one heck of a mis-match, no wonder you were disapointed with dual subs. Mongo like BFD, Mongo want's BFD now!

[kexodusc]

Well, that 20 dB is kinda misleading...there's a couple small narrow peaks not accounted for in the graph on the way down that slope, but yeah, an aweful lot of info lost. .
The old PW-2200 didn't go near as low despite Paradigm's specs, but I'll give that sloppy ported bastard credit, it, because it rolled off the overall slopiness wasn't quite as dramatic. I think my room has a few troublesome nodes that are sucking bass out....and I get that double peaking in the low 30's and mid 20's.
My ceiling isn't flat either, maybe this is messing things up...

Sounds awesome now!!! I'm hearing all the notes. I think the house-slope will be even better, wonder if anyone around's tried that?

[PAT.P]

Kexodusc Can this BFD work when Im using 2 sub? What about the cross over setting on receiver?Pat.P

[hmmmm]

There is software you can download, however, it really isn't that bad. If you can build a speaker and sub, you can figure this thing out. Not to mention there's 47 years of experience with this unit lurking here on the forums, that's all the help you'd ever need.

If you have a Radio Shack SPL meter, download some test tones and check out the response of your sub between 20 and 90 Hz. You'll be surprised what room acoustics do. If your response curve is as bad as mine was (or heaven forbid, worse), you owe it to yourself.

I do lose a couple of dB's from my cheapo Toshiba DVD-A/SACD player. That's normal though, probably just a different output sensitivity (ie: voltage). My Arcam CD player is also a bit louder than most of my other units. So is my X-Box.

Don't worry about turning up your receiver any, the numbers in the display are arbitrary and don't necessarily mean that the amplifiers are at max.

I have the radio shack spl meter. I'll test it out. I do have a pretty normal "rectangle" room with a couple of entrances that can be closed off with doors and one hallway that has an extremely thick curtain that I pull closed to seal the room as good as I can. I have a few bass traps that made a big difference also. I'll let you know what happens when I get a chance to test the fifteen incher

[hmmmm]

Where is a good place to download the test tones? I don't recall my Avia disk having the 20-90 test tones in increments. A friend of mine has it at the moment.

[Woochifer]

Looking at that before and after curve, it seems that you've done a fine job with your first set of parametric filters! Seeing that huge contrast right in the middle of your original response curve would single-handedly ruin whatever aspirations to accurate bass you might have had.

Your testimonial just adds to the increasing list of "best $100 I've spent on my system" praises for that Behringer Feedback Destroyer. Even without additional tweaking, just getting rid of those two large peaks and that big dip in your bass response alone would be enough to vastly improve the quality of your bass.

One thing I would add. The BFD adds 1-2 ms of delay onto the signal, so you might want to decrease the distance of your subwoofer on the setup menu from the receiver accordingly. The flatter and more even frequency response has already worked wonders on my bass. Since my older receiver locks everything in at Yamaha's old 90 Hz crossover point, and does not allow for any delay compensation on the subwoofer, I think those are really the only adjustments remaining that I need to make.

[kexodusc]

Wooch - I had a lot of help from a few people by e-mail with way more experience than me...but I still have at least 14 hours of tinkering on this thing. As I mentioned, there's still a few problematic areas that just don't show up on the plot because of the 1/6 octave intervals in data entry, so this curve looks better than it really is (I should be marketing speakers) but yeah, the difference is incredible.

My curve is really more of a semi-eliptical shape. I'd like to try the so-called house-curve to compensate for my hearing (and add some fun-factor to movies).
My room is over 500 square feet in an odd sort of shape, but rectangular for the most part. The sloped ceiling at one end probably adds some trouble as well, the living room at my last place didn't produce nearly as problematic a response curve.
As for delay, you're about the 14th person that's mentioned that to me. The BFD has a huge on-line fan-club, another benefit that really helps with the learning curve.

Wooch, couldn't you compensate for the lack of delay on your sub by reducing delay on the other 5 speakers? Isn't it all relative? Just a shot.

[Woochifer]

Wooch, couldn't you compensate for the lack of delay on your sub by reducing delay on the other 5 speakers? Isn't it all relative? Just a shot.

Can't do it because my receiver does not alter the timing for the main channels. Only the center and surround speakers have adjustable delay. The subwoofer is unfortunately locked in with the mains.

The ability to tweak with the settings and create a house curve is one of the fun aspects of having up to 12 parametric filters to play around with. I tweak with my system every few months and experiment with other settings to see what other bass response curves float my boat.

[kexodusc]

Can't do it because my receiver does not alter the timing for the main channels. Only the center and surround speakers have adjustable delay. The subwoofer is unfortunately locked in with the mains.

The ability to tweak with the settings and create a house curve is one of the fun aspects of having up to 12 parametric filters to play around with. I tweak with my system every few months and experiment with other settings to see what other bass response curves float my boat.

Your receiver sounds like my old RX-V795a all over again. Though I do miss the knob controls that unit had, much more personal than digital settings.

Any recommendations for attacking the house curve? I'm thinking that increasing the sub-amp's gain and cutting frequencies with filters at 6 db/octave or so is the safest bet, but I have enjoyed some success with boosting some frequencies. It be nice if I could just undo some of the cuts below 40 Hz and let it go. I'll use program 5 for that.

[Woochifer]

Your receiver sounds like my old RX-V795a all over again. Though I do miss the knob controls that unit had, much more personal than digital settings.

Mine's the RX-V800, basically the successor to the 795, except with Yamaha's then new digital Top-ART design, which put a lot more setup options into the on-screen setup menus.

Any recommendations for attacking the house curve? I'm thinking that increasing the sub-amp's gain and cutting frequencies with filters at 6 db/octave or so is the safest bet, but I have enjoyed some success with boosting some frequencies. It be nice if I could just undo some of the cuts below 40 Hz and let it go. I'll use program 5 for that.

Generally, the advice is to use the BFD for attenuation only. Especially with low level signals, the BFD's known for adding a layer of noise and coloration to the signal. Might want to play around with the gain and just use the filters for cutting the signals, and create your curve that way. Isn't this fun?

I guess what I like the most about using the BFD is how well it illustrates the link between what the technical measurements say you're supposed to hear, and what you actually hear.